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Akkermansia muciniphila is a Gram-negative anaerobic bacterium, a component of the normal human intestinal microbiota. A decrease in the presence of this bacterium is associated with pathologies, including metabolic disorders, intestinal inflammation and colorectal cancer. A. muciniphila is a probiotic approved for patients with diabetes and obesity. In recent years, A. muciniphila was studied in the control of intestinal inflammation and colorectal cancer. The exact mechanisms of A. muciniphila action remain unclear, while the use of different administration protocols shows different effects in mouse models of colitis and colorectal cancer. We reported that A. muciniphila has distinct effects on intestinal mucin production depending on viable or pasteurized form of bacteria. Another factor affecting the outcome of the A. muciniphila administration is the number of bacteria. To address how the dose of bacteria may affect the severity of acute intestinal inflammation wild-type mice were subjected to daily oral injections with 10⁸ CFU or 109 CFU of viable A. muciniphila for two weeks; the control group was injected with PBS. After that, groups were subjected to the induction of acute colitis by adding 7% DSS to drinking water for five days. 8 days after the onset of colitis induction, a morphometric assessment of the colitis severity was performed. Mice given a high dose of A. muciniphila (109 CFU) were found to be protected from developing severe colitis. RT-PCR analysis of colon samples from mice receiving a high dose of bacteria showed an increase in the gene expression of antimicrobial peptides, IL-17A, IL-17F. Interestingly, the protective effect of A. muciniphila was observed only in a high dose group, but not in a low dose group. Our data suggest that A. muciniphila provides the protective effect in colitis and highlight the importance of selecting the dose of the bacterium for proper interpretation.
Sheynova et al. (Sun,) studied this question.